US20020044343A1 - Control system for optical amplifiers and optical fiber devices - Google Patents
Control system for optical amplifiers and optical fiber devices Download PDFInfo
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- US20020044343A1 US20020044343A1 US09/907,305 US90730501A US2002044343A1 US 20020044343 A1 US20020044343 A1 US 20020044343A1 US 90730501 A US90730501 A US 90730501A US 2002044343 A1 US2002044343 A1 US 2002044343A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/29—Repeaters
- H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
- H04B10/293—Signal power control
- H04B10/294—Signal power control in a multiwavelength system, e.g. gain equalisation
- H04B10/2942—Signal power control in a multiwavelength system, e.g. gain equalisation using automatic gain control [AGC]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/1301—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/1301—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers
- H01S3/13013—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers by controlling the optical pumping
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S2301/00—Functional characteristics
- H01S2301/04—Gain spectral shaping, flattening
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
- H01S3/06758—Tandem amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
- H01S3/10015—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by monitoring or controlling, e.g. attenuating, the input signal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
- H01S3/10023—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by functional association of additional optical elements, e.g. filters, gratings, reflectors
- H01S3/1003—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by functional association of additional optical elements, e.g. filters, gratings, reflectors tunable optical elements, e.g. acousto-optic filters, tunable gratings
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
- H01S3/302—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects in an optical fibre
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- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
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Abstract
An optical feedback control system utilizes one or more linear photodiode arrays to map the optical characteristics of an optical signal at a plurality of different wavelengths over an entire communication spectrum. The data gathered from the linear photodiode arrays is actively used to control gain and gain flatness of a fiber optic amplifier system or other optical fiber device, such as a fiber laser.
Description
- The instant invention relates to control systems for dynamically controlling gain and gain flatness in optical fiber devices, and more particularly to an optical feedback control system utilizing one or more linear photodiode arrays to map the optical characteristics of an optical signal at a plurality of different wavelengths over an entire communication spectrum. The data gathered from the linear photodiode arrays is actively used to control gain and gain flatness of a fiber optic amplifier system or other optical fiber device.
- Most fiber optic amplifiers already utilize a control system for controlling average gain of the amplifier, and other parameters of operation. In the past, a portion of the transmission signal would be tapped off of the transmission line and fed to an individual photodiode to analyze a particular parameter of the signal. In other cases, the signal would be tapped at two separate points in the transmission line and fed to two photodiodes for comparison. One tap would be located before the amplifier block and the other tap after the amplifier block. The desired parameter measured from the two photodiodes, for example signal strength, would be compared and used to control laser diode power which, in turn, would allow control of average gain of the optical signal strength. The photodiodes provide a means for measuring what happens to the optical signal in the amplifier as changes are made and thus provide a means for controlling operation of the amplifier. The inherent limitation of simple photodiodes is that they can only be used to measure a single wavelength at a given time. While this was acceptable in older transmission systems where the usable wavelength band was fairly narrow, newer wavelength division multiplexed (WDM) transmission systems require a uniform gain profile over a far greater bandwidth so that each usable wavelength in the transmission spectrum is uniformly amplified. The use of conventional measurement and control systems has made monitoring and control of WDM transmission systems difficult.
- As the industry seeks to expand the number of usable wavelengths in WDM transmission systems, the gain flatness of an optical amplifier across the entire transmission spectrum has become one of the most important characteristics of an amplifier, even more important than the overall gain. In this regard, other passive and active components, such as dynamic gain flattening filters (GFF's) and variable optical attenuators (VOA's), have been added to the amplifier systems to flatten the gain curve. However, even with these new devices, changing input signal strength and other variable factors in operation still make it difficult to dynamically control gain flatness over a broad spectrum of wavelengths.
- Accordingly, while the existing control systems are effective to a limited extent, they do not provide the flexibility or spectral range required for a true dynamically controlled gain flattened amplifier system. There is thus a need in the industry to provide a control system that can actively measure the gain profile of the entire operating spectrum of the input signal so that the entire gain curve of the amplifier can be controlled more efficiently.
- The instant invention provides a control system that employs at least one Linear Indium Gallium Arsenide Photodiode Array for monitoring the entire transmission spectrum and a microcontroller programmed with appropriate software, and control parameters for controlling the optical amplifier system. The microcontroller is connected to the diode laser pump(s) of the amplifier, active gain-flattening filters (GFF's) and the variable optical attenuators (VOA's). The transmission signal is tapped from the transmission line by an optical tap and fed to the linear photodiode array for analysis. The linear photodiode array is effective for analyzing the entire spectrum of the transmission signal. In basic terms, the photodiode array functions as a spectrum analyzer for analyzing the entire transmission system in an active control system. Based on information provided and the control parameters, the microprocessor can be programmed to control the laser diodes, filters and attenuators to control and flatten the output of the amplifier responsive to slight variations in the optical signal.
- Accordingly, among the objects of the instant invention are: the provision of an improved means for analyzing the entire spectrum of an optical transmission signal from a single or multiple tap source(s); the provision of an improved control system which utilizes linear photodiode arrays to analyze the spectral characteristics of an optical transmission signal and which uses the information provided to control the various components of the amplifier system; the provision of such a control system wherein the optical signal is tapped at point that precede the amplifier, follow the amplifier and/or both; and the provision of such a control system which is effective for controlling the pump sources, gain flattening filters and variable optical attenuators of a complex optical amplifier system.
- Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.
- In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:
- FIG. 1 is a graphical illustration of average optical gain of an amplifier as measured by a conventional photodiode at a single wavelength;
- FIG. 2 is a graphical illustration of an optical gain curve as measured by a linear photodiode array at multiple wavelengths, as part of the control system of the present invention;
- FIG. 3 is a schematic illustration of a single-stage Erbium-doped fiber optic amplifier employing the control system of the present invention;
- FIG. 4 is a schematic illustration of a dual-stage Erbium-doped fiber optic amplifier employing the control system of the present invention;
- FIG. 5 is a schematic illustration of a fiber laser employing the control system of the present invention; and
- FIG. 6 is a schematic illustration of a Raman fiber optic amplifier system employing the control system of the present invention.
- Referring now to the drawings, the optical device control systems of the instant invention are illustrated and generally indicated10 in FIGS. 3-6.
- As will hereinafter be more fully described, the
instant control systems 10 utilize one or more linear photodiode arrays 12 to map the optical characteristics of an optical signal at a plurality of different wavelengths over an entire communication spectrum. - Referring to FIG. 1 of the drawings, there is shown a graphical illustration of the gain curve of an erbium-doped amplifier as measured by a prior art photodiode system. The prior art typically measured average gain of the amplifier by measuring the gain at a central wavelength in or about the middle of the amplified wavelength spectrum, i.e. in or about 1540 nm to about 1550 nm. The resulting graph is a bell-shaped curve that shows signal strength decreasing to each side of the central measured wavelength. While the single sampling of information from this wavelength was effective for determining the maximum gain of the amplifier at a central wavelength of the amplified spectrum, the actual shape of the gain curve at lower and higher wavelength is much more complex and is not accurately represented by a single sampling of data at a central wavelength. As the industry seeks to expand the number of usable wavelengths in WDM transmission systems, the gain flatness of an optical amplifier across the entire transmission spectrum has become one of the most important characteristics of an amplifier, even more important than the overall gain.
- Referring to FIG. 2, there is shown a graphical illustration of the actual shape of the gain curve of the same erbium-doped amplifier as determined by a sampling of data from a plurality of wavelengths along the entire amplified spectrum. As can be seen from the graph, there is a slight hump at the lower end of the spectrum and the higher end of the spectrum drops off somewhat steeper than as represented by the average in FIG. 1. As indicated above, the industry has continually sought an amplifier that has a flat gain profile over the broadest possible wavelength band. By flat gain, we mean that the amplifier has a gain profile that has a relatively flat plateau of the same gain across a wide band. Such a curve is illustrated in broken line in FIG. 2. In this regard, other passive and active components, such as dynamic gain flattening filters (GFF's) and variable optical attenuators (VOA's), have been added to existing amplifier systems to flatten the gain curve to the greatest extent possible. However, even with these new devices, changing input signal strength and other variable factors in operation still make it difficult to dynamically control gain flatness over a broad spectrum of wavelengths. The data gathered from the linear photodiode arrays12 as taught by the present invention, is actively used to control gain and gain flatness of a fiber optic amplifier system or other optical fiber device, such as a fiber laser.
- It is pointed out that erbium doped fibers are described herein as representative examples and as part of the preferred embodiments. However, it should be understood that the principles and concepts herein are equally applicable to other amplifier systems and other optical devices using other types of rare-earth doped fibers and using Raman amplification effects.
- Referring now to FIG. 3, a single-stage Erbium-doped fiber optic amplifier constructed in accordance with the teachings of the present invention is illustrated and generally indicated at14. The
amplifier 14 is spliced into a conventionaloptical transmission fiber 16 configured to propagate an optical transmission signal. Theamplifier 14 includes a length of erbium dopedfiber 18 that is spliced into thetransmission fiber 16 using an input wavelength division multiplexer (WDM)coupler 20, and anoutput WDM coupler 22. Theamplifier 14 is pumped by a laserdiode pump laser 24 of appropriate wavelength and power to stimulate emissions of the erbium ions in the desired transmission wavelength range. Theamplifier 14 further includes anoptical isolator 26 preceding theinput WDM coupler 20, a dynamic gain flattening filter (GFF) 28 following theoutput WDM coupler 22, and further includes a variable optical attenuator (VOA) 30 following theGFF 28. Theoptical isolator 26, GFF 28 and VOA 30 are conventional amplifier components that are commercially available from multiple sources. Accordingly, no further description or explanation of the function of these devices is believed to be necessary. - With regard to the
control system 10 of theamplifier 14, thepump laser 24, GFF 28 and VOA 30 are each electronically connected to amicrocontroller 32 which is programmed with appropriate software and control parameters to adjust and control these active components during operation. Microcontrollers and microprocessors of the type contemplated for use herein and the software for programming their operation are well known in the electronics arts. Thecontrol system 10 of the present invention is preferably based on a comparative analysis of information as taken from two separate points in thetransmission fiber 16. Accordingly, the preferred embodiment as shown in FIG. 3 comprises first and secondlinear photodiode arrays amplifier 14, the input optical transmission signal is tapped from thetransmission fiber 16 by anoptical tap 34 and is provided to the firstlinear photodiode array 12A for analysis. On the output side of theamplifier 14, the amplified optical transmission signal is tapped from thetransmission fiber 16 following theVOA 30 by a secondoptical tap coupler 36, and is provided to the secondlinear photodiode array 12B for analysis. The twolinear photodiode arrays linear photodiode arrays microcontroller 32 can more effectively control thelaser diode 24,GFF 28 andVOA 30 to control the output of theamplifier 14. The use of twolinear photodiode arrays amplifier 14 and thus leads to improved control. - In the present embodiment, the two
linear photodiode arrays active erbium fiber 18 of theamplifier 14. However, it is to be understood that the signal can be tapped anywhere in thetransmission line 16, depending on the circumstances and design of theamplifier 14, and it is to be understood that a single linear photodiode array 12 could be used in a basic arrangement with similar effectiveness. In this regard, a single tap could be located preceding the erbium-dopedfiber 18 or following the erbium-dopedfiber 18. - Referring now to FIG. 4, a dual-stage erbium-doped fiber optic amplifier constructed in accordance with the teachings of the present is illustrated and generally indicated at38. The dual-
stage amplifier 38 includes a first stage amplifier system generally indicated at 40 having the same general components as thesingle stage amplifier 14 as illustrated in FIG. 3, and further includes a second stage amplifier system generally indicated at 42 that also includes the same general set of component elements. More specifically, the firststage amplifier system 40 comprises a length of erbium-dopedfiber 44 that is spliced into thetransmission fiber 16 using an input wavelength division multiplexer (WDM)coupler 46, and anoutput WDM coupler 48. Thefirst amplifier stage 38 is pumped by a laserdiode pump laser 50 of appropriate wavelength and power to stimulate emissions of the erbium ions in the desired transmission wavelength range. Thefirst amplifier stage 38 further includes anoptical isolator 52 preceding the input WDM coupler46, a dynamic gain flattening filter (GFF) 54 following theoutput WDM coupler 48, and further includes a variable optical attenuator (VOA) 56 following the GFF. The secondstage amplifier system 42 similarly comprises a length of erbium dopedfiber 58 that is spliced into thetransmission fiber 16 using an input wavelength division multiplexer (WDM)coupler 60, and anoutput WDM coupler 62. Thesecond stage amplifier 42 is pumped by a laserdiode pump laser 64 of appropriate wavelength and power to stimulate emissions of the erbium ions in the desired transmission wavelength range. Thesecond stage amplifier 42 further includes anoptical isolator 66 preceding theinput WDM coupler 60, a dynamic gain flattening filter (GFF) 68 following theoutput WDM coupler 62, and further includes adelay circuit 70 and anotheroptical isolator 72 following the GFF. - The
pump lasers VOA 56 are each electronically connected to amicrocontroller 74 which is programmed with appropriate software and control parameters to adjust and control these active components during operation. Thecontrol system 10 further comprises first and secondlinear photodiode arrays transmission fiber 16 as previously described hereinabove usingoptical tap couplers first photodiode array 12A is positioned between theVOA 56 on the output side of thefirst stage 40 and theoptical isolator 66 on the input side of thesecond stage 42. On the output side of theamplifier 38, the amplified optical transmission signal is tapped from thetransmission fiber 16 following thesecond GFF 68, and is provided to the secondlinear photodiode array 12B for analysis. - As in the single-
stage amplifier system 14, the twolinear photodiode arrays laser diodes VOA 56 to control the output of the amplifier stages 40, 42. - Turning now to FIG. 5, it is also to be understood that the
present control system 10 could be used effectively for controlling the operation of a distributed feedback (DFB) fiber laser as well. In this regard, a fiber laser constructed in accordance with the teachings of the present invention is illustrated and generally indicated at 80 in FIG. 5. As will hereinafter be more fully described, the DFBfiber laser assembly 80 comprises a single mode, rare-earth doped optical fiber generally indicated at 82 having a Bragg grating 84, and a light source generally indicated at 86 coupled to thefiber 82. - The doped
optical fiber 82 is well known in the fiber optic arts, and is available from any one of a variety of commercial sources. Thefiber 82 is doped with a rare earth ion, such as erbium, to provide a stimulated light emission as pump light passes through the dopedfiber 82. Thefiber 82 is provided with a uniform Bragg grating 84. The creation of Bragg gratings in optical fibers is well known in the art, and will not be described further herein. The grating 84 is written into thefiber 82 so that thefiber 82 produces an output with a desired wavelength as is common in the art of DFB fiber lasers. It is desirable to keep the length of thefiber 82 short, and in this regard it is preferred that the length of thefiber 82 be limited to between about 2 cm to about 6 cm. Reflectivity of the grating 84 is generally determined by the lasing wavelength, the dopant level and the length of the fiber. Thepreferred fiber 82 should have a length between about 2 cm and about 6 cm, and have a reflectivity of about 90%. - The
light source 86 comprises any known, or unknown, light source having an output wavelength within the rare-earth absorption spectrum. Such light sources include, but are not limited to semiconductor laser diodes, as well as other light sources. In keeping with the previously discussed erbium-doped fiber example, a representative light source comprises a 50 mW semiconductor laser diode having a 980 nm or 1480 nm wavelength output. - With regard to the
control system 10, the optical signal is preferably tapped from the fiber laser construction at two points usingoptical tap couplers laser diode 86 and the input of dopedfiber 82, and between the output of the dopedfiber 82 and anoptical isolator 92. The tap coupler output is provided to thelinear photodiode arrays laser source 86 and the photodiode arrays 12 are connected to amicrocontroller 94 as described above. Based on information provided and a comparison of the two gain profiles, themicrocontroller 94 can more effectively control thelaser diode 86 to control the output of thefiber laser 80. - Even further still, referring to FIG. 6, the control system of the present invention is applicable for use in a Raman amplifier. In this regard, a Raman amplifier constructed in accordance with the teachings of the present invention is illustrated and generally indicated at96 in FIG. 6. A
typical Raman amplifier 96 comprises a anoptical transmission fiber 16 configured to have an optical signal propagate therethrough, abackward pumping module 98 configured to pump light into theoptical transmission fiber 16 and a WDMoptical coupler 99 that optically interconnects thepump module 98 with thetransmission fiber 16. The optical signal is preferably tapped from thetransmission fiber 16 at two points. Afirst tap coupler 100 is located at the input oftransmission fiber 16, and asecond tap coupler 102 is located at the output of theWDM coupler 98. Thepump module 98, andlinear photodiode arrays - It can therefore be seen that the present invention provides a unique and novel control arrangement for controlling the operation of a variety of optical fiber devices. The linear photodiode arrays12 as used in the present systems provide improved data and analysis of the input signal profile and gain profile of the amplifier systems over the entire communication spectrum rather than a single operating wavelength. These linear photodiode arrays 12 are operable in real time and can provide a real time analysis of the operation of an amplifier system allowing real-time adjustment of operating parameters in order to quickly control and compensate for fluctuating input signals and other variable factors during operation. For these reasons, the instant invention is believed to represent a significant advancement in the art which has substantial commercial merit.
- While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.
Claims (31)
1. An optical amplifier system comprising:
an optical transmission fiber configured to have a WDM optical transmission signal propagate therethrough,
a rare-earth doped fiber optic amplifier configured to amplify said transmission signal, said amplifier including a pump source;
an optical tap configured to extract a portion of said transmission signal;
a linear photodiode array configured to receive said extracted portion of said transmission signal, said linear photodiode array detecting an optical characteristic of said transmission signal at a plurality of wavelengths; and
a controller configured to control said pump source to flatten a gain profile of said optical amplifier system responsive to an output received from said linear photodiode array.
2. The optical amplifier system of claim 1 wherein said optical tap coupler precedes said amplifier.
3. The optical amplifier system of claim 1 wherein said optical tap coupler follows said amplifier.
4. The optical amplifier system of claim 1 further comprising a dynamic gain flattening filter (GFF) following said amplifier, said controller being configured to control said pump source and said GFF responsive to said output received from said linear photodiode array.
5. The optical amplifier system of claim 1 further comprising a variable optical attenuator (VOA) following said amplifier, said controller being configured to control said pump source and said VOA responsive to said output received from said linear photodiode array.
6. The optical amplifier system of claim 4 further comprising a variable optical attenuator (VOA) following said amplifier, said controller being configured to control said pump source, said GFF and said VOA responsive to output received from said linear photodiode array.
7. The optical amplifier system of claim 2 further comprising a second optical tap following said amplifier and configured to extract a portion of said amplified transmission signal; and
a second linear photodiode array configured to receive said extracted portion of said amplified transmission signal, said linear photodiode array detecting an optical characteristic of said amplified transmission signal at a plurality of wavelengths of said transmission signal,
wherein said controller is configured to control said pump source to flatten a gain profile of said optical amplifier system responsive to outputs received from said linear photodiode arrays.
8. The optical amplifier system of claim 7 further comprising a dynamic gain flattening filter (GFF) following said amplifier, said controller being configured to control said pump source and said GFF responsive to said outputs received from said linear photodiode arrays.
9. The optical amplifier system of claim 7 further comprising a variable optical attenuator (VOA) following said amplifier, said controller being configured to control said pump source and said VOA responsive to said outputs received from said linear photodiode arrays.
10. The optical amplifier system of claim 8 further comprising a variable optical attenuator (VOA) following said amplifier, said controller being configured to control said pump source, said GFF and said VOA responsive to said outputs received from said linear photodiode arrays.
11. A dual-stage optical amplifier system comprising:
an optical transmission fiber configured to have a WDM optical transmission signal propagate therethrough,
a first rare-earth doped fiber optic amplifier configured to amplify said transmission signal, said first amplifier including a first pump source;
a second rare-earth doped fiber optic amplifier configured to further amplify said transmission signal, said second amplifier including a second pump source;
a first optical tap following said first amplifier and preceding said second amplifier configured to extract a portion of said transmission signal;
a first linear photodiode array configured tp receive said extracted portion of said transmission signal, said first linear photodiode array detecting an optical characteristic of said transmission signal at a plurality of wavelengths;
a controller configured to control said first and second pump sources to flatten a gain profile of said dual-stage optical amplifier system responsive to outputs received from said first and second linear photodiode arrays.
12. The dual-stage optical amplifier system of claim 11 further comprising a second optical tap coupler following said second amplifier and configured to extract a second portion of said transmission signal and a second linear photodiode array configured to receive said second extracted portion of said transmission signal, said second linear photodiode array detecting an optical characteristic of said transmission signal at a plurality of wavelengths of said transmission signal, wherein said controller is configured to control said first and second pump sources to flatten a gain profile of said dual-stage optical amplifier system responsive to said outputs received from said linear photodiode arrays.
13. The dual-stage optical amplifier system of claim 11 further comprising a first dynamic gain flattening filter (GFF) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump sources and said GFF responsive to said output received from said linear photodiode array.
14. The dual-stage optical amplifier system of claim 11 further comprising a variable optical attenuator (VOA) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump sources and said VOA responsive to said output received from said linear photodiode array.
15. The dual-stage optical amplifier system of claim 13 further comprising a variable optical attenuator (VOA) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump source, said GFF and said VOA responsive to output received from said linear photodiode array.
16. The dual-stage optical amplifier system of claim 13 further comprising a second dynamic gain flattening filter (GFF) following said second amplifier, said controller being configured to control said pump sources and said GFF's responsive to said output received from said linear photodiode array.
17. The dual-stage optical amplifier system of claim 16 further comprising a variable optical attenuator (VOA) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump source, said GFF's and said VOA responsive to output received from said linear photodiode array.
18. The dual-stage optical amplifier system of claim 12 further comprising a first dynamic gain flattening filter (GFF) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump sources and said GFF responsive to outputs received from said linear photodiode arrays.
19. The dual-stage optical amplifier system of claim 12 further comprising a variable optical attenuator (VOA) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump sources and said VOA responsive to outputs received from said linear photodiode arrays.
20. The dual-stage optical amplifier system of claim 18 further comprising a variable optical attenuator (VOA) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump source, said GFF and said VOA responsive to outputs received from said linear photodiode arrays.
21. The dual-stage optical amplifier system of claim 18 further comprising a second dynamic gain flattening filter (GFF) following said second amplifier, said controller being configured to control said pump sources and said GFF's responsive to outputs received from said linear photodiode arrays.
22. The dual-stage optical amplifier system of claim 12 further comprising a variable optical attenuator (VOA) following said first amplifier and preceding said second amplifier, said controller being configured to control said pump source, said GFF's and said VOA responsive to outputs received from said linear photodiode arrays.
23. A distributed feedback fiber laser assembly comprising:
a rare-earth doped optical fiber having a grating;
a pump source configured to pump light into said doped optical fiber and stimulate emissions from said doped optical fiber;
an optical tap configured to extract a portion of said pump light;
a linear photodiode array configured to receive said extracted portion of'said pump light, said linear photodiode array detecting an optical characteristic of said pump light at a plurality of wavelengths; and
a controller configured to control said pump source to control an output profile of said fiber laser responsive to an output received from said linear photodiode array.
24. The fiber laser of claim 23 further comprising a second optical tap following said doped optical fiber and configured to extract a portion of said stimulated emissions from said optical fiber, and a second linear photodiode array configured to receive said extracted portion of said stimulated emissions, said second linear photodiode array detecting an optical characteristic of said stimulated emissions at a plurality of wavelengths of said transmission signal,
wherein said controller is configured to control said pump source to control an output profile of said fiber laser responsive to outputs received from said first and second linear photodiode arrays.
25. A Raman amplifier system comprising:
an optical fiber configured to have an optical signal propagate therethrough;
a pump source configured to pump light into said optical fiber and Raman-amplify with said pump light said optical signal;
an optical tap configured to extract a portion of said optical signal;
a linear photodiode array configured to receive said extracted portion of said optical signal, said linear photodiode array detecting an optical characteristic of said optical signal at a plurality of wavelengths; and
a controller configured to control said pump source to flatten a gain profile of said optical amplifier system responsive to an output received from said linear photodiode array.
26. The Raman amplifier system of claim 25 wherein said optical tap precedes an input of said optical fiber.
27. The Raman amplifier system of claim 25 wherein said optical tap follows an output of said optical fiber.
28. The Raman amplifier system of claim 26 further comprising a second optical tap following an output of said optical fiber and configured to extract a portion of said amplified optical signal, and a second linear photodiode array configured to receive said extracted portion of said amplified optical signal, said second linear photodiode array detecting an optical characteristic of said amplified optical signal at a plurality of wavelengths of said optical signal, wherein said controller is configured to control said pump source to control an output profile of said Raman amplifier system responsive to outputs received from said first and second linear photodiode arrays.
29. A method of controlling an optical device having an optical fiber configured to propagate an optical signal and further having at least one adjustable optical component, said method comprising the steps of:
extracting a portion of said optical signal from said optical fiber;
providing said extracted portion of said optical signal to a linear photodiode array;
determining an optical characteristic of said optical signal at each of a plurality of different wavelengths using said linear photodiode array;
controlling said at least one adjustable optical component responsive to said optical characteristic of said optical signal as determined by said linear photodiode array.
30. The method of claim 29 wherein said at least one adjustable optical component is selected from the group consisting of: a pump source, an active gain flattening filter, and a variable optical attenuator.
31. A method of controlling an optical amplifier system having an optical fiber configured to propagate an optical signal and an amplifier configured to amplify said optical signal, said amplifier further having a pump source, said method comprising the steps of:
extracting a first portion of said optical signal from said optical fiber at a location preceding said amplifier;
extracting a second portion of said optical signal from said optical fiber at a location following said amplifier;
providing said first extracted portion of said optical signal to a first linear photodiode array;
providing said second extracted portion of said optical signal to a second linear photodiode array;
determining an optical characteristic of said first and second portions of said optical signals at each of a plurality of different wavelengths using said first and second linear photodiode arrays;
controlling said pump source responsive to said optical characteristics of said optical signals as determined by said linear photodiode arrays.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/907,305 US20020044343A1 (en) | 2000-07-17 | 2001-07-17 | Control system for optical amplifiers and optical fiber devices |
Applications Claiming Priority (2)
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US21858800P | 2000-07-17 | 2000-07-17 | |
US09/907,305 US20020044343A1 (en) | 2000-07-17 | 2001-07-17 | Control system for optical amplifiers and optical fiber devices |
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US20020044343A1 true US20020044343A1 (en) | 2002-04-18 |
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ID=22815686
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US09/907,305 Abandoned US20020044343A1 (en) | 2000-07-17 | 2001-07-17 | Control system for optical amplifiers and optical fiber devices |
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US (1) | US20020044343A1 (en) |
AU (1) | AU2001282901A1 (en) |
WO (1) | WO2002007272A2 (en) |
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Also Published As
Publication number | Publication date |
---|---|
WO2002007272A3 (en) | 2002-04-11 |
AU2001282901A1 (en) | 2002-01-30 |
WO2002007272A2 (en) | 2002-01-24 |
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